1. Field of the Invention
This invention relates to disc players for selectively playing back one of small and large size discs and, more particularly, to disc centering devices for centering small size discs in the same disc players.
2. Description of the Prior Art
In a disc player for selectively playing back one of large and small size discs, in which either a small or a large size disc is centered with respect to a turntable by causing engagement of a clamper having a tapered surface in the center hole of the disc, the extent of disc insertion has to be changed according to the diameter or size of the inserted disc. The regulation of the extent of insertion of each disc is made by bringing the disc edge into contact with paired, i.e., left and right, small or large size disc stoppers. The large size disc stoppers are disposed rearwards relative to the small size disc stoppers in the disc inserting direction. Therefore, in the case of the large size disc insertion, the paired small size disc stoppers have to be caused to escape from the insertion path for the large size disc.
Japanese Patent Disclosure 2003-257109 discloses a disc centering device. In this device, paired left and right rockable disc sensor members have integral leading members, respectively, which also serve as small size disc stoppers. When the center of a small size disc inserted from a disc insertion slot slightly passes by the center of a turntable, the edge of the small size disc strikes the small size disc stoppers. As a clamper engages in the center hole of the small size disc, the small size disc is slightly pulled back by a tapered surface of the clamper to be separated from the small size disc stoppers, whereby the disc is centered relative to the turntable.
The disc is suitably inserted such that its center proceeds along a line passing through the axis of the turntable, which line is referred to as “disc insertion center line L”. However, since the disc insertion slot is formed such that the large size disc can also be inserted through it, it is liable that the small size disc is deviated laterally as it is inserted. Excessive deviation of the disc in lateral direction may disable a disc centering operation by the tapered surface of the clamper.
This means that the leading members which also serve as small size disc stoppers, should be disposed at positions, at which the leading members fulfill both a function of limiting or regulating the extent of insertion of the small size disc and a function of guiding the small size disc, having been inserted in lateral deviation with respect to the disc insertion center line L, such that the center of the small size disc proceeds along the disc insertion center line L.
For limiting or regulating the extent of insertion of the small size disc, the leading members are desirably disposed at positions in the neighborhood of the disc insertion center line L. Doing so, however, poses a problem. That is, when the small size disc is inserted in a laterally deviated state, it may be disabled to guide the small size disc such that the center thereof proceeds along the disc insertion center line L.
In the meantime, for guiding the small size disc such that the center thereof proceeds along the disc insertion center line L, the leading members are desirably disposed such as to be laterally spaced apart from the disc insertion center line L as much as possible. However, commercially available discs slightly fluctuate in diameter, and in the case of insertion of a small size disc having a less diameter than the standard, the more the leading members are spaced apart from the disc insertion center line L, the more is the excessive insertion extent until the small size disc strikes the leading members. In this case, it is liable that the small size disc can no longer be pulled back by the tapered surface of the clamper.
As shown above, it is very difficult to set the positions of the leading members such as to fulfill both the function of limiting or regulating the extent of insertion of the small size disc and the function of correcting the deviation of the small size disc. Accordingly, it may be considered to set a long tapered surface of the clamper enough to be able to effect the centering even when the center of the small size disc is greatly deviated from the center of the turntable. By so doing, however, the extent of displacement of the clamper is increased to increase the size of the device.
The invention seeks to solve the above problems, and its object is to provide a disc centering device for both large and small size discs, which permits a centering operation of the small size disc relative to the turntable with the clamper without increasing the extent of displacement of the clamper.